The C.sub.60 molecule was originally discovered as a peak in the mass spectra of quenched carbon vapor. To explain the stability of this molecule, Kroto et al., "C.sub.60: Buckminsterfullerene", Nature, 318 (1985) 162-163, first proposed the structure of a truncated icosahedron, a polygon with 60 vertices and 32 faces, 12 of which are pentagonal and 20 hexagonal, commonly encountered as a soccer ball, and dubbed Buckminsterfullerene.
Kratschmer et al., "Solid C.sub.60 a new form of carbon", Nature, 347 (1990) 354-358, pioneered the electric arc method for generating fullerenes, such as C.sub.60 and C.sub.70, which has since become the standard technique.
A simple modification of this technique, increasing the buffer gas, helium, pressure from 100 torr (13,332 Pa) to 500 torr (66,661 Pa), resulted in the formation of carbon nanotubes, as reported by Ajayan et al in "Large-scale synthesis of carbon nanotubes", Nature, 358 (1992) 220-222. The carbon nanotubes consist of nested concentric tubes of carbon where each tube is made up of curved graphite-like sheets of carbon. The tubes are hollow on the inside and the ends of the tube are usually sealed with fullerene-like caps The tubes have a high aspect ratio with the diameter being in the range from 2 nanometers to several tens of nanometers and the length being as long as several microns. The same technique for generating carbon nanotubes can also generate giant fullerene-like carbon clusters first reported by Ugarte, Nature, 359 (1992) 707-709. Irradiation with an electron beam can convert the tubes to concentric hollow spheres made of carbon. These carbon clusters are polygonal in shape and have onion-like structures, consisting of nested polygons of carbon layers.
It has been found possible to open carbon nanotubes with chemical methods as reported by Tsang et al., "Thinning and opening of carbon nanotubes by oxidation using carbon dioxide", Nature, 362 (1993) 522-525. Tsang et al. opened the tubes by heating them in carbon dioxide at 850.degree. C. Ajayan et al. opened the tubes by heating the tubes in air above about700.degree. C.
When the end of carbon nanotubes is open, lead has been successfully included in the tube by simply dipping the tube end into molten lead as reported by Ajayan et al., Nature, 361 (1993) 333-334. Lanthanum carbon has been placed inside nested giant carbon clusters using the electric arc method as reported by Ruoff et al., Science, 259 (1993) 346-348.
The present invention provides for the encapsulation of palladium crystallite inside worm-like carbon nanostructures, as well as, giant carbon clusters from which the worm-like carbon nanostructures are formed.